CONTENTS. y 



Gekehai, Physics, 



Mr. Robert Stawell Ball's Account of Experiments upon tlie Resistance 

 of Air to the Motion of Vortex-rings 20 



Mr. H. Deacon's Experiments on Vortex-rings in Liquids 29 



Professor J. D. Everett on Units of Force and Energy 29 



Dr. J. H. Gladstone and Alfred Tribe on the Corrosion of Copper Plates 

 by Nitrate of Silver 29 



M. Janssen's Remarks on Physics 29 



INIr. T. M. Lindsay and W. R. Smith on Democritus and Lucretius, a Ques- 

 tion of Priority in the Kinetical Theory of Matter 30 



Professor James Thomson's Speculations on the Continuity of the Fluid State 

 of Matter, and on Relations between the Gaseous, the Liquid, and the Solid 

 States 30 



Observations on Water in Frost Rising against 



Gravity rather than Freezing in the Pores of Moist Earth 34 



Astronomy. 



Professor Cliffobd on the Secular Cooling and the Figure of tbe Earth .... 34 



Dr. Gill's Observations on the Parallax of a Planetary Nebula 34 



M. Janssen on the Coming Solar Eclipse 34 



Mr. J. Norman Lockyer on the Recent and Coming Solar Eclipses 34 



Mr. R. A. Proctor on the Construction of the Heavens 34 



Professor Osborne Reynolds on Artificial Coronas 34 



Mr. H. Fox Talbot on a Method of Estimating the Distances of some of the 



Fixed Stars 34 



Professor Charles V. Zenger on the Nutoscopo, an Apparatus for f^howing 



Graphically the Curve of Precession and Nutation 30 



Light. 



Mr. Philip Braham's description of a Set of Lenses for the Accurate Cor- 

 rection of Visual Defect 37 



Mr. Thomas'Stevenson's description of a Paraboloidal Reflector for Light- 

 houses, consisting of silvered facets of ground-glass ; and of a Diflereutial 

 Holophote ■. "T 



Professor G. G. Stokes's Notice of the Researches of the late Rev. William 

 Vernon Harcoui-t' on the Conditions of Transparency in Glass, and the Con- 

 nexion between the Chemical Constitution and Optical Properties of dif- 

 ferent Glasses 38 



Mr. G. Johnstone Stoney on one Cause of Transparency ........ r ....... . 41 



on the advantage of referring the positions of 



Lines in the Specti-um to a Scale of Wave-numbers 42 



Professor William Swan on the Wave-lengths of the Spectra of the Hydro- 

 carbons - 43 



The Abbe Moigno on the Poste Photographique .■ 44 



Mr. R. Sutton's Accoimt of a New Photographic Dry Process 44 



